Note: Descriptions are shown in the official language in which they were submitted.
FIELD OF THE INVE~TION
This invention relates to the electric heating
of automobile engines during cold weather condition3.
More par-ticularly, the inventiorl relates to an electric
heating element which is placed within an engine bLock
through a frost plug, and the temperature control oE the
heater using a unique arrangement that integrates an
engine block thermo~tat to the block heater.
BACKGROUND OF THE INVE~TION
Presently, a~tomobiles which use electrical
block heaters during cold weather conditions are simply
plugged in to an electrical outlet as required. There
is no control over electrical po~er consumption or
engine temperature. With a fixed electrical current
draw, engine temperatures can be higher than required
for effective engine starting, thus wasting energy.
Further, block heaters may be plugged in unnecessarily
on days when a block heater i9 not needed, thereby
contributing to energy waste. For instance, an
~ automobile owner could plug in his block heater for a
full day unnecessarily because he was predicting cold
weather for the next day, when in fact it might turn out
to be mild. His tendency would at most -times be to err
on the conservative side, thus leading to a waste of
energy. By way of specific example, on the coldest
night of the year in Saskatchewan (-30C -to ~40C),
virtually every vehicle would have its block heater
plugged in for the night to an electrical power source
as soon as the driver parked the vehicle, usually before
the dinner hour. This would be the case even though
tests under such temperatures have clearly shown that
because of residual heat stored in the engine block
the block heater need not be pluyged in until the engine
had been stopped for at least Eour hours. IE the
plug-in was made at about 18()0 hours, Eor example, 500
to 750 W of electrical power draw per automobile would
be unnecessarily added to the peak load oE the
electrical utility at that time of day. This can be a
signiEicant problem for the electrical utility when tens
oE thousands of heaters are plugged in at approximately
the same time. The problem is compounded because it
generally occurs when power draw by the public is at its
peak due to lights and stoves being turned on in
preparation Eor dinner.
Several thermostatically controlled block
heater designs are known to the applicant but most are
temperature controlled using a bellows apparatus that
expands when heatedO Gratsinger (United States Patent
No. 2,505,286) uses a bimetal temperature control but it
is connected to a heater that is external to the block
of the engine and is for temporary installation only.
As well, devices are on the market that
attempt to attenuate the block heater load~ For
example, a device called Power Saver Cord* is manufact-
ured and sold by Temro Automotive, Winnipeg, Manitoba.
These devices measure the engine coolant temperature in
the heater hose and switch the block heater ON and OFF
accordingly. But this device is an "add-on" type~ which
is an inconvenience and a nuisance. ~lso, measurement
of the engine block temperature is not taken.
*Trade Mark
-- 2 --
S[lM;lAR~ OF THE INVENTION
The applicant's invention comprises a thermo-
stat and a block heater integrated as one unit with only
a small increase in overall si7e compared to a conven-
tional block heater.
The invention is directed to an apparatus for
heating liquid~cooled, automotive engines adapted for
installation in an opening in the coolant-containing
jacket of the engine block wherein the apparatus is an
integral unit comprising a body member adapted to seal
the opening and having an electric heating element moun-
ted thereon to extend into the interior o~ the engine
block~ a thermostat electrically connected to the
heating element and responsive to the temperature of the
engine block to electrically connect the heating element
to a source of electric energy when the temperature of
the engine block is below a lower limit and to discon-
nect ~he heating element from the source of electric
energy when the temperature o~ the engine block is above
an upper limit, means for thermally isolating the ther-
mostat from the electric heating element and means for
securing the apparatus in the opening. According to one
aspect of the invention, the apparatus may further
include heat-conducting means to conduct heat ~rom the
engine block to the the~mostat which may be a base
element on which the th0rmostat is mounted and which is
adapted to directly contact the jacket of the engine
block when the apparatus is installed in the engine
block. The apparatus may be installed in a frost plug
of the internal combustion engine block. A hollow space
formed in the body member or heat-insulating material
may comprise the means for thermally isolating -the ther-
mostat. According to a ~urther aspect of the invention,
-- 3 --
,
-the apparatus may comprise a housing to externally cover
the thermostat and isolate it from external ternperature
changes. Further, the apparatus may be secured in the
opening by means oE a retaining bar adapted to be c~rawn
against the i.nterior surface of the jacket adjacent the
opening upon tightening of an external nut on a bolt
p~ssing through the retaining bar and the apparatus~
DRAWINGS
In the drawings:
FIGURE 1 represents two graphical depicti.ons
of ~ngine Block temperature against Engine Temperature
Cooldown Rate with Ambient Air Temperatures respectively
of -20C and -30C;
FIGURE 2 represents a side elevation view of
the integrated device;
FIGURE 3 represents a frontal elevation view
of the integrated device;
FIGURE 4 represents a section view taken along
Section A-A of FIGURE 3;
FIGURE 5 represents a section view taken along
Section B B of FIGURE 2; and
FIGURE 6 represents a graphical depiction of
Ambient Air Temperature against Thermostatic Block
Heating Temperature Histories.
FIGURE 7 represents a graphical depiction of
Ambient Air Temperature, Block Surface Temperature and
Power Consump-tion against Time.
DETAILED DESCRIPTION OF THE INVENTION
FIGURE 1 represents a graphical depiction of
rate of engine temperature cool down at two di~ferent
ambient temperatures (-20C and -30C). Results are
shown for eight cylinder, six cylinder and four cylinder
eng.ines. r~1e cool down rate is slower for e.ight
cylil1der engines presumabl~ because of larger enc,sine
size (gre~l-ter heat capacity) an(l larger coolant volurne.
The graphs of experimen-tal results demonstrate that the
5. average ~ime for the englne temperature to cool -from
~pproximately 70C to ~10C at the respective ambient
temperatures is about four hours. An engine can usually
be started readily at temperatures above -10C. Thus,
when the block heater is plucsced in at any time duriny
10 this cool down period, even at an ambient telrlperature o~
~30r'C, energy ls wasted~
The invention, as shown in FIGURES 2 and ~,
consists o a cornbina-tion of an electric heatirl~
elemen-t l, shielding insulation 2, a heat conducting
disc 3, a thern1ostat 4 and wiring 5 to conrlect Lhe
thermostat 4 in series with the heater l. The
therlnostat 4 uses a bimetal disc or strip to open a set
of electrical current points or co1tacts ~not shown)
. which are h~!at sensi~ive and can be set to interrupt the
: ~0 electrical current at a prescribed block temperature,
~or example, about 0C. The means by which the current
is controlled by the thermostat 4 is lesi-~ned for small
ss?aces an~ is available from a nurnber of sources. For
exalnple, Texas Instruments Incorporated distributes
~5 various ~ixed ternperat~re thermostats which are designed
for use where space is limited.
FIG~5RES 3 and 5 show respectively ~.rorltral
elevatio-1 and section views of -the inventlor1, incl~l(.1ing
clelnerlt l, disc 3, t'hern~ostclt 4/ holdlll~3 dlsc 6 and
30 retainincs ~ar 8.
-- 5 --
~ .
As seen in FIGURE 4, the invention is ti~htly
helcl in ~ sized circular hole in the en~ine block 10 by
a holding disc 6 (sized to :Eit into the hole in the
engirle block 10), a retaining bol.t 7 extending throuyh
the block 10 (by way of sleeve 13) and a retaininc3 bar 8
on ~he inside of the block :lO penetrated by the bolt 7,
and a butterfly nut 17. An O-ring g is fitted between
the block 10 and di.sc 6 to ensure a liquid tight engine
coolant seal. ~ sealing washer 12 i8 also used to
preveot en~ine coolant leaking khrough the sleeve 13.
~he therrnostat 4 is held in place by an enclosin~
cover 11 (preferably cons-truc-ted of rubber or plastic~
and a retaining nut i5. In-ternal retaining nut 16 i5
used to hold together the inner assembly which consists
1.5 of the heat conductin~ plate 3, the insulat.ing
material 2 and the holding disc 6. Retaining bar 8 is
longer .in length than the diameter of the circu].ar hole
opening and thereby firmiy fastens the device -to the
en~ine block 10 when butter-Ely nut 17 is securely
~0 tight2ned. Re-taining bar 8 is also suffici~ntly short
to allow it to be inserted into the circular hole
openiny upon installation.
The function of insulation 2 and dead ai.r
space 14 in combination is to isolate the heater element
~5 1. and en~ine coolant from -the heat conducting disc 3
which is in direct contact with block 10. Insul~ltion 2
may be a r:igid fibrous glass insulating l~aterial which
has su~er:ior insulating properties. Other insulating
materiaLs which can tolerate en~ine block temperature
ancl provide superior insulatlon quali~i.es may be used.
. ~, . . .
p~ ,.
The s~ace L4 can also be packed with a sui-table
insulating material, either the s~me as or lifferent
from insulat:ion 2~ With a conventional block heater,
tests have shown ~hat sensing the temperature on the
heater flange of the block heater tencls to provide a
localize~ readin~ ~nd to thereby inhibit proper cycling
of the heater. Because only a locali~ed warm portion is
being sensed, the.heater tends to be shut oEE before the
overall engine block and coolant are up to temperature
(-10C). By insulating heat conduction from the hea-ter
element 1 and the coolant t.o the conducting disc 3,
thermostat 4 tends not to be sensitive to local heating
caused by the heater element 1 but tends t.o be sensi.tive
to the overall block temperature, whicll tends ~o be
relAtively close to the average coolan-t temQerature.
The thermostat 4 is also isolated from the
cold ambient air ternperature by the rubber or plastic
cover 11, thereby reducing the sensitivity o~ the
: therlnostat 4 ~o outside temperatures, and erl3uring that
t.he thermostat 4 more closely measures engine block 10
and coolant temperature.
Example 1
The thermostatically controlled block heater
was installed in a 4~cylinder engine block in order to
test i-ts response to changes in envirollment -temperature.
The engine block was instrumented with thermocouples and
the power to the block heater monitored continuousLy
during tests that were conducted in an envrironmental
chamber. FLG~RE 7 shows the results oE reducing the
ellvironlnental chamber temperature in s-teps Erom -10C to
_ 7 _ .
~,
%
-40C. It was observed that the surface -temperature of
the engin~ block wa~ maintained between 0 and -10C by
the cycling of the thermos-tat. Also, as the ~nvi.ronment
temperature was reduced, the duty cycle of the block
heater increased, thereby responding to the increased
heating load on the block.
The surface temperature of the enyine block
shown in FIGURE 7 was chosen -to represent the average
tempera-ture o the block. In fact, because of natural
convection, the hotter coolant rises to the top and the
colder coolant settles at the bottom of the block
resulting in stratification in temperatures. In
addition, the block heater itself is a localized h.igher
temperature area.
Table 1
Block Heater Response Due to Changing Temperature
Environment Duty Cycle Percent Coolant Temperature
Chamber Time Time O~ ApproxO
Temperature O~ OFF Time Average Min. Max.
(F) (C) (min.) (min.) (%) ~C) (C) _C)
12 -11 2.0 60 3 -10 -12
14 -10 2.0 35 5 - 8 - 9
0 -17 2~0 6.8 23 - 7 -11 6
3 -16 2.0 7.2 22 - 4 -11 8
-12 ~24 2.6 3.6 42 - 7 -12 7
-1~ -27 2.8 3.2 47 - 7 -13 3
-2~ -33 4.0 2.6 60 - 7 -16 5
-40 -40 7.2 2.0 78 - 8 -17 4
As shown in Table 1, with the unit used, the
tests indicate that the -thermostatically controlled
block heater will maintain the engine coolant
~7~
temperature between -17C and -~8~ ~or all environmental
chamber temperatures.
The device, by its desi~n, controls the
coolant temperature in the engine block to a temperature
within the range -10C to 10C, which is usually
suficiently hiyh to promote easy engine starting. By
not permittin~ the engine to reach temperatures higher
than necessary for s-tart.i.ng, energy is conse:rved. In
fact, because o~ heat stored in the engine block,
the block heater in -30C weather does not as a rule
consume electricity for about ~ hours after the engine
has been stopped. Consequently, because most auto-
mobiles are "plugged in" after driving home ~rom the
of.ice, the use of the applicant's device proportion-
; 15 ately reduces the peak load drawn on the elec-trical
:~ power utility (a most desirable objective from the
taxpayer's and ut.ility's point oE view)~
The upper and lower temperature limits o~ the
thermostat may be changed as required thereby altering
the duty cycle and the energy consumption of the
device.
The applicant's device is a distinct improve-
ment on the presently available add-on thermostat
devices because the customer cannot easily disconnect or
remove the thermostat component. This might happen on
very cold days, for example, because the owner, in
taking the saEe approach, may not trust an add-on device
and simply disconnect i-t. He does this at the precise
time that max.imum power draws are being made on the
electrical power utility. Power draws tend to be
largest on the coldest days. Further, the reduced cost
of production of one device compared to two means lower
initial and installation costs to the cu~tomer. The
unit package is not significantly larger than present
commercially acceptable bloclc heaters and this should
result in higher customer acceptance because the device
can be installed in place o~ existing block heaters.
Some specific benefits of this unique
combination are:
(l) '~le integral device has higher
reliability and ]ower maintenance;
(2) The device can be easily installed at
reduced cost because the device is
unitary in construction (inte~rated block
heater and thermostat) and is installed
as a unit instead of two separate units
(block heater and add-on thermostat);
(3) The device enables direct and accurate
measurement of the engine block
~ temperature to be made by insulating the
thermostat and temperature sensing plate
from th0 heater element and the ambient
environment;
(~) The device remains in place with the
vehicle for use whenever the vehicle is
plugged in;
(5) The device maintains engine block
temperature at a level necessary for
starting (~10C to -10C) and not higher,
thereby conserving energy;
-- 10 ~
(6) No electrical power demand is normally
made at peak use periods because the
device does not draw curren-t whi.le there
is a pre-determi.ned level of residual
S heat in the block for -those vehicles
driven home from work at noon time or in
the eveni.ng;
(7) The device is moun-ted within the block
thereby minimi.zing heat loss as compared
to an externally mounted block heater;
and
(8) The device, being small and compact can
be fitted into most automobiles in place
of an existing block heater.
As will be apparent to those skilled in the
art in the light of the foregoing disclosure, many
alterations and modiEications are possible in ~he
practice of this invention without departing from the
spirit or scope thereof. Accordingly, the scope of the
invention is to be construed in accordance with the
substance deined by the following claims.
